Technical units are all types of technical devices and systems both arranged individually and networked for data purposes, e.g. via a field bus. In the case of industrial applications these include individual operating means, e.g. drives, processing machines. However a technical unit can also be a production unit, in which an overall technical process is operated using locally distributed operating means, e.g. a chemical unit or production line. Technical units are controlled and operated using specific digital data processing systems, also referred to as automation components. In such a system on the one hand there are components used for direct control of the technical unit, i.e. programmable logic controllers PLC. To reduce the load on these controllers, automation systems have further specific devices, which form an interface for operating personnel. These are referred to as control and monitoring devices or HMI or Human Machine Interface devices.
The term HMI device is a generic term covering all components associated with this group of devices. One example is operator panels or OPs. These can be stationary or mobile. HMI devices are used in networked automation as aids for operating personnel so that they can display and control process data of the technical unit to be controlled. This function is referred to as Supervisor Control and Data Acquisition (SCADA). To this end the HMI device generally has specific hardware. In other words it has a touchscreen for example and is specifically screened from environmental influences. Specific software is also operated therein. This provides functions, which enhance user-friendliness, quality and safety of operation by an operator. Thus HMI devices can be used to visualize, control, configure and generate interactive process maps of the technical unit to be operated. On the one hand this allows the selective display of responses of the technical unit, generally in the form of measured values and messages. On the other hand the customized predefinition of control operations and data inputs allows the technical unit to be switched to required states.